Various types of guiding arrangements for tapes retained in cassettes in which the tape is spooled from a reel positioned in a first plane on a reel positioned in a second plane parallel thereto, for example in an arrangement in which a pay-out reel and a take-up reel in a cassette are located above each other. Such cassettes are described, for example, in German published patent application DE-AS No. 12 41 141. To guide the tape from one plane to another, a plurality of fixed guide pins are provided, the guide pins having bowed or curved guide surfaces and flanges at both sides of the guide surfaces in order to guide the tape from a reel in a first plane to a reel in a plane parallel thereto, for example above or below the first reel.
German published patent application DE-AS No. 21 31 731 describes a tape cassette having coaxially arranged reels, in which the cassette has a guide track, and an opening therein which is diagonal/parallel to a narrow side of the cassette. A semi-cylindrical fixed guide track is provided which has a pair of flanges in order to guide the magnetic tape from the plane of one reel to the plane of the other reel, for example immediately above or below the first reel.
Cassettes of this type have the disadvantage that the frequent deflection of the tape leads to increased friction of the tape on the guide elements, which causes flutter or wow in reeling of the tape, in other words, which interferes with uniform, smooth movement of the tape at a fixed predetermined speed. The edges of the magnetic tapes are very thin, and if the guide elements are not precisely aligned, and carefully and accurately polished, damage to the fragile edges of the tapes may result. This is particularly annoying in tape cassettes in which the magnetic tape is so used that its operating direction can change. If the tape is to operate in either a first or a reverse direction, the accuracy of guidance must be high, and damage to the edges of the tape must be avoided.
In order to decrease friction of the tape on a guide surface, it has been proposed to utilize rolling elements. One such cassette is described, for example, in U.S. Pat. No. 3,294,334. A magnetic tape is guided from a reel in one plane to a reel in another plane. The path of the tape includes a guide track which also has the respective scanning elements thereon. By suitable choice of the run-on and run-off in which the tape runs, it is possible to so guide the tape that it operates approximately centrally on guide elements which are formed with flanges. Due to tolerances within the magnetic tape, particularly upon reverse spooling, it is possible that the tape position changes, and differs from the tape position when the tape was running in a forward direction, for example by engaging opposite flanges on a flanged roller in dependence on the direction of movement of the tape. When using high-density recording, the magnetic tape can thus shift laterally, which may lead to loss of reproduction of previously recorded tracks.
German Pat. No. 883,557 describes the use of conically constructed partial drum elements which are used to center thin tapes, and which thereby are intended to avoid fixed or rotating lateral guide structures, thus eliminating damage to the edges of the tape while centering the tape on the drum. The thicker ends of the conical partial drum elements face each other. The drum elements are journalled elastically on a continuous shaft, roughly at the center of gravity of any one of the elements, so that the circumferential surface may adjust itself automatically under tension of the tape to an approximately cylindrical guide path. Due to the resulting return forces, the tape tends to run in the middle of the overall arrangement, regardless of the direction of rotation. Both tape portions are driven in synchronism.
Application of a centering or otherwise directional force by the tape itself can be obtained by separating a roller used to deflect the tape in V-shape--see German published patent application DE-AS No. 10 38 477--and to offset the respectively facing ends of the rollers outwardly in that direction which is in the same plane as the resulting tension force for the tape. This applies a directional force on the tape which counteracts a tendency of lateral creep of the tape from a central position.
Guidance of elongated tapes, typically recording carriers adapted for magnetic transducer apparatus, can also be carried out by using frusto-conical rollers which are located on respectively mutually inclined shafts, and to locate the ends of the frusto-conical roller elements which are smaller adjacent each other--see German published patent application DE-AS No. 12 82 701.